[sv-bc] $unit::m or $root.m in module instance?

It might be useful, in the presence of nested modules, to
specify a module name in a module instantiation using $unit
or $root:

    module top();
        $unit::m1 u1();
	$root.m2 u2();
    endmodule

The lrm says that the module name in a module_instantiation
has to be an identifier.  This rules out using $unit::<id>
and $root.<id> as module names.  I wonder if this
restriction is intentional.

Paul